Updated the test system

test/compose.test.js

@@ -0,0 +1,15 @@
+const expect = require('expect');
+const {compose} = require('./_30s.js');
+
+test('compose is a Function', () => {
+  expect(compose).toBeInstanceOf(Function);
+});
+const add5 = x => x + 5;
+const multiply = (x, y) => x * y;
+const multiplyAndAdd5 = compose(
+  add5,
+  multiply
+);
+test('Performs right-to-left function composition', () => {
+  expect(multiplyAndAdd5(5, 2)).toBe(15);
+});